Optical tables are used for supporting optical and other analytical devices, for example lasers, that must be mounted on extremely rigid flat surfaces. Bending or twisting of the surface of the table must be minimized in order to minimize displacement of the devices relative to one another.
Historically, granite slabs have been used as optical tables. While these tables provide flatness and rigidity required in an optical table, their great weight and the difficulty of attaching components to their surfaces make them cumbersome to use.
Modern optical tables are generally of composite construction consisting relatively thin upper and lower metallic skins bonded to central honeycomb core which is enclosed by a surrounding sidewall. Typically, the top surface or skin of a honeycomb optical table is furnished with a regular array of threaded mounting holes to permit the secure attachment of optical fixtures and related devices to the table top. The cost of such composite construction optical tables can be thousands of dollars. When laser dyes, oils, coolants, beverage spills, and other debris enter the interior honeycomb core section of such an optical table through the apertured table top, the result can be disastrous. Because of the bonded construction of such honeycomb tables, they can not be disassembled for cleaning. Liquids, vapors, and particles that enter the interior of the table during manufacture or later use can also escape rendering the optical table incompatible with clean room requirements.
There are various prior art methods of constructing honeycomb core optical tables which limit the entry of contaminates into the interior honeycomb core of the optical table.
For example, the optical table shown in FIG. 1A is disclosed in U.S. Pat. No. 5,154,963. Flat sealing sheet 10, FIGS. 1A and 1B, separate honeycomb core section 12 from honeycomb core section 14 and thus any contaminates spilled through aperture 16 in top table leaf 18 will be sealed off from honeycomb core section 14 via sealing sheet 10. One problem with such a structure is the requirement of two honeycomb core sections 12 and 14, the addition of sealing sheet 10, and the manufacturing inconveniences associated with the same.
The honeycomb table construction shown in FIG. 2A, disclosed in U.S. Pat. No. 5,061,541, includes corrugated sheet 20, FIGS. 2A and 2B, which seals orifices 16 in table top 18 with respect to honeycomb core 14. Stiffening sheet 22, adjacent to corrugated sheet 20, is required in the preferred embodiment for structural rigidity. Again, the inconvenience of properly orienting and assembling corrugated sheet 20 and the need for stiffening sheet 22 can be disadvantageous.
The optical table shown in FIG. 3A is disclosed in detail in U.S. Pat. Nos. 5,021,282 and 4,853,965. Sealing sheet 30, FIGS. 3A and 3B, includes a number of downward projections such as projection 32 which individually seals each cavity of honeycomb core 14 with respect to orifices 16 in table leaf 18. In this design, the complexity of stamping or vacuum forming sealing sheet 30 as well as the difficultly of manufacturing an optical table including such a sealing sheet renders the design less than desirable. In addition, to clean such an optical table, each honeycomb cavity must be individually cleaned using a vacuum line connected to each aperture in the table leaf.